Field of the Disclosure
The present disclosure relates generally to imaging device media sensors and methods of using the same, and more particularly to media stiffness sensors and methods of using the same.
Description of the Related Art
Currently, most imaging devices require user to input media type, weight, and texture. However, most users do not adjust media settings. Of those that do adjust settings, only a small percentage correctly classify media. Failure to correctly set media properties results in print quality defects, poor fuse grade, and higher jam rates. Also, this leads to a higher number of service calls, visits, and replacement part rates.
Incorrectly setting media weight is a major contributor to these higher failure rates. If the media weight is set too low, the printer runs too fast, transfer voltages are set too low, and fuser temperatures are set too low. If the media weight is set too high, the printer runs too slow, transfer voltages are set too high, and fuser temperatures are set too high. Poor print quality is a result along with premature hardware failures.
In particular, light weight media set at a normal or a heavy weight has a much higher likelihood to wrap a fuser, particularly, when printing higher coverage pages. Too much heat is provided and the toner hot offsets. Because the trend is towards using lighter weight media with more refined (recycled) fiber content, this problem will become more prevalent.
Additionally, heavy weight media set at normal or light weight does not adequately melt the toner and cold offset occurs. This allows unattached toner to deposit on the fuser backup roll and be carried downstream where it contaminates paper guides and creates catch points. This results in a higher likelihood for jams, fuser being wrapped by media (fuse wraps), and machine damage on subsequent jobs. Ultimately, if media is run at an improper weight setting, user satisfaction suffers.
A number of sensors that loosely correlate to stiffness or thickness are available. These include methods based upon wave/pulse transmission (optical, acoustic, microwave, etc.), visual thickness inspection (cameras mounted in a tray, etc.), and monitoring feed or pick motor current. Energy transmittance methods typically have difficulty distinguishing between very light and normal weight media; these methods also have broader standard deviations when the media is more porous, is dual-web, or has a watermark. Visual thickness inspection would require camera electronics and hardware to be placed in each media input and image processing algorithms would be needed to interpret the data captured. Feed motor and pick motor current signals are inherently noisy; the current is dependent upon sheet friction, bending stiffness, and the dynamic behavior of the sheet.
It would be desirable to have a sensor and method that avoids the aforementioned drawbacks and provides an automatic determination of a media weight of a sheet of media as it is being fed along a media feed path in an imaging device prior to being imaged. It would additionally be desirable to be able to adjust an operating parameter of the imaging device based on the selected media weight.